Frequently Asked Questions about Stainless Steel

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About Stainless Steel

Here are answers to the most common questions we receive about stainless steel.

Stainless Steel is all around us, it is used for benches, tapware, ovens, rangehoods... Stainless steel is the generic name for a number of different steels used primarily because of their corrosion resistance. All stainless steels share a minimum percentage of 10.5% chromium. It is this element that reacts with the oxygen in the air to form a complex chrome-oxide surface layer that is invisible but strong enough to prevent further oxygen from "staining" (rusting) the surface.

The film itself is extremely thin, about 130 Angstroms and one Angstrom is one millionth of a centimeter. This layer is described as passive, tenacious and self-renewing. Higher levels of chromium and the addition of other alloying elements such as nickel and molybdenum enhance this surface layer and improve the corrosion resistance of the stainless material. Furthermore, stainless steel is fully recyclable.

The three major classes of stainless steel are:

  • Austenitic: Chromium-nickel-iron alloys with 16-26% chromium, 6-22% nickel, low carbon content, non-magnetic if annealed. Type 304 ("18/8") is the most common.
  • Martensitic: Chromium-iron alloys with 10.5-17% chromium, controlled carbon, magnetic, used in knives. Type 420 is typical.
  • Ferritic: Chromium-iron alloys with 17-27% chromium, low carbon, magnetic. Type 430 is common.

Additional classes include Duplex and Precipitation Hardening stainless steels for extreme conditions.

Chrome-Nickel content refers to the percentage of chrome and nickel in the stainless steel. Chrome gives the stainless steel its luster & durability, while nickel adds hardness & strength. 18/10 Stainless Steel means it contains 18% Chromium and 10% Nickel. A sink with 18/10 chrome-nickel content is considered excellent grade due to its corrosion resistance and durability.

18/8 means 18% chromium and 8% nickel. 18/10 means 18% chromium and 10% nickel. Higher numbers mean more corrosion resistance. Both are part of the 300 series (non-magnetic). 18/0 means 18% chromium and zero nickel, part of the 400 series (magnetic, less corrosion resistant).

304 contains 18% chromium and 8% nickel. 316 contains 16% chromium, 10% nickel and 2% molybdenum. The molybdenum improves resistance to chlorides such as sea water and de-icing salts making it more applicatable to marine hardware.

Yes. Stainless steel is easily welded, but the procedure differs from carbon steel. The filler rod or electrode must be stainless steel.

Stainless steel has excellent properties at both extremes. Some grades can be used down to liquid nitrogen temperatures, others up to about 1800°F.

Stainless steel can be recycled 100%. Typically, 65–80% of new stainless steel is made from recycled scrap.

Stainless does not rust in the same way as regular steel. Corrosion is generally caused by contaminants settling on the surface of the stainless steel, rather than the steel itself breaking down.

The 300 series (which contains nickel) is not magnetic. The 400 series (which contains chromium but no nickel) is magnetic.

Austenitic stainless steels are tough and resist scaling, commonly used in knives and cooking utensils. Ferritic and austenitic grades are used in kitchenware and household appliances, with austenitics preferred in the food industry for superior corrosion resistance.

Type 301, for example, is widely used for institutional food preparation utensils. High quality cookware often uses Type 304 with thick heat-diffusing bottoms, sometimes bonded with copper or aluminum.

Cutlery varies: lower quality uses ferritic grades like 409 and 430, while high-end cutlery uses martensitic grades like 410 and 420 for knives and austenitic 304 for spoons and forks.

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